Flexible lensed optical interconnect device for signal distribution

ABSTRACT

A method and device for interconnecting optical components, such as optical fibers and optical circuits, in a flexible, repeatable, and cost- effective manner. Two or more optical components are interconnected by a flexible optical circuit substrate bearing one or more embedded optical fibers with a lens at each end of each fiber. The flexible optical circuit may be incorporated into a housing bearing apertures for receiving the optical connectors of the optical components that are to be interconnected with the device. The lensed ends of the fibers embedded in the flexible optical circuit are positioned adjacent to the apertures for optically connecting to the fibers within the connectors installed in the apertures without conventional mating connectors disposed inside the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.17/022,890, filed Sep. 16, 2020; which is a continuation of U.S.application Ser. No. 16/653,253, filed Oct. 15, 2019, now U.S. Pat. No.10,782,483; which is a continuation of U.S. application Ser. No.16/027,946, filed Jul. 5, 2018, now U.S. Pat. No. 10,451,809; which is acontinuation of U.S. application Ser. No. 15/236,054, filed Aug. 12,2016, now U.S. Pat. No. 10,031,295; which is a continuation of U.S.application Ser. No. 13/230,094, filed on Sep. 12, 2011, now U.S. Pat.No. 9,417,418, the disclosures of which are hereby incorporated it theirentireties.

FIELD OF THE INVENTION

The invention pertains to fiber optic connectivity for high speed signaldistribution.

BACKGROUND OF THE INVENTION

Fiber optic breakout cassettes are passive, optical components thatconnect fibers between sets of cables. Such cassettes usually providedtransition between multi-fibered connectors, such as MPO type connectorswith MT ferrules, and single or dual fiber connectors, such as LC or SCtype connectors. A typical fiber optic breakout cassette of the priorart is illustrated in FIG. 1. The function of this particular exemplarycassette 100 is to distribute the signals between the twelve fiberscontained in fiber optic cable 103 and six dual-fiber cables 105. Forinstance, in a practical case, each dual-fiber cable 105 comprises onetransmit channel and one receive channel. Hence, six of the fibers inthe twelve-fiber cable 103 transmit data into and through the cassetteto one of the fibers in each of the six dual-fiber cables 105. The othersix fibers in the twelve-fiber cable 103 receive data through thecassette from the other one of the fibers in each of the six dual-fibercables 105. Thus, multi-fiber cable 103 is terminated with a multi-fiberconnector, such as an MPO plug connector 107. The six dual fiber cables105 are each terminated with a dual fiber connector, such as dual fiberLC plug connectors 109. Alternately, each cable 105 could be terminatedwith two signal-fiber connectors. The cassette 100 comprises adapter 114in an aperture in the wall of the housing 101 to which a twelve-fiberMPO-style receptacle connector 111 is attached on the inside of thehousing for mating with the twelve-fiber MPO-style plug connector 107 atthe end of cable 103. The cassette 100 further comprises six dualadapters 115 in apertures in the wall of the housing 101 to which twelvesingle-fiber LC-style receptacle connectors 113 are attached on theinside of the housing 101 for optically connecting to the six dual-fiberLC-style plug connectors 109 at the ends of fiber optic cables 105.Twelve individual fibers 117 are routed within the housing 101 betweenthe back of the MPO receptacle connector 111 and the backs of the twelveLC receptacle connectors 113.

These optical cassettes 100 are rather expensive because they usuallyare assembled by hand by highly skilled workers and require connectionof the fibers 117 to the connectors 111 and 113 at both ends of eachfiber, which includes placing the fibers 117 into the ferrules ofconnectors 111, 113, epoxying the fibers in the connectors, polishingthe end faces of the fibers, routing the fibers 117 within the tightspace of the housing 101, and all the other steps normally associatedwith optical fiber terminations to connectors. Further, because thecassettes are hand-assembled, they are subject to human error andvariability depending on operator skill and experience, especially withrespect to improper fiber routing. In addition, assembly of a fiberoptic cassette involves time-consuming, in-process testing, especiallyfor higher speed components.

Even further, with the increasing prevalence of 40 GB and 100 GB persecond optical networks, the breakout/consolidation in a fiber opticcassette involves multi-fiber connectors on both ends of the fiberssince, in 40 GB and 100 GB networks, each channel now includes 4, 8, 10,or 20 fibers in parallel, rather than 2. With the channels now needingmany more fibers, consolidation of these channels into larger fibercount trunks will be critical in the future as space inside data centersbecomes more costly. As a consequence, the associated fiber routinginside the cassette becomes much more complex and prone to operatorvariability.

Power requirements for optical channels will be strict and spaceconstraints will be significant. Hence, performance will need to betightly controlled, such that tolerances will become increasingly strictand operator variability will become more and more problematic. Thiswill lead to more costly, higher precision components, higher in-processtesting costs, and increased levels of manufacturing rework and scrap.

SUMMARY OF THE INVENTION

The invention relates to a method and device for interconnecting opticalcomponents, such as optical fibers, optical connectors, and opticalcircuits, in a flexible, repeatable, and cost-effective manner. Theinvention can be implemented in optical cassettes, patch panels, patchpanel enclosures, zone distribution hardware, wall fixtures, and thelike. It may be used to replace breakout cables in data centers and thelike. It may be applied in virtually any optical interconnectivityapplication. In accordance with the invention, two or more opticalcomponents are optically interconnected by a flexible optical circuitsubstrate bearing one or more embedded optical fibers with a lens ateach end of each fiber. The lens may be embedded in the flexible opticalcircuit substrate or disposed in a separate supporting device eithermounted on or apart from the substrate. The flexible optical circuit maybe incorporated into a housing bearing apertures for receiving theoptical connectors of the optical components that are to beinterconnected with the device, such as the optical connectors at theends of optical cables or at the interfaces of optical orelectro-optical circuits. The cleaved ends of the fibers embedded in theflexible optical circuit or in a subsidiary device are positionedadjacent to lenses which allow optical coupling to the apertures foroptically connecting to the fibers within the connectors installed inthe apertures without the need for mating connectors inside of thehousing. Alternately, fibers may be shaped such that they act as lensesto couple directly to a focusing device such as a lens to opticallycouple to the connectors mounted in the apertures.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an exemplary fiber optic cassette of the priorart with the top panel removed.

FIG. 2 is a depiction of a flexible fiber optical circuit in accordancewith the principles of the present invention.

FIG. 3 is a plan view of a fiber optic cassette in accordance with theprinciples of the present invention with the top panel removed.

FIG. 4 is a detailed view of portion A of FIG. 3.

FIG. 5 is a diagram illustrating an embodiment of the invention used formaking optical connections between patch panels in an equipment rack.

FIG. 6 is a diagram illustrating the principles of the present inventionincorporated into a variable depth rack mount enclosure.

FIG. 7 is a depiction of a variable depth cassette in accordance withone embodiment of the invention.

FIG. 8 is a depiction of another cassette in accordance with theprinciples of the present invention that is flexible.

FIG. 9 is a depiction of yet another cassette in accordance with theprinciples of the present invention that is bendable about a hinge.

FIG. 10 is a depiction of an optical splitter in accordance with theprinciples of the present invention.

DETAILED DESCRIPTION

The present invention relates to a method and apparatus forinterconnecting first and second optical components, such as opticalcables or electro-optical devices in a cost-effective, flexible, andrepeatable manner. The invention is particularly suitable in suchapplications as optical cassettes, patch cables, optical splitters,patch panel interconnectors, zone distribution hardware, wall fixtures,and the like.

The present invention involves the use of flexible optical circuitsbearing at least one, but, more effectively, many optical fibersembedded in a flexible optical circuit substrate with a molded lensdisposed on at least one end face of the one or more fibers. The lensescan be optically interfaced with external standard optical connectors(e.g., MPO, LC, ST, SC plugs) at the ends of cables or at the interfacesof electro-optical devices without the need for a conventional matingconnector (e.g., MPO, LC, ST, SC receptacles). Rather, a connector on anoptical component, e.g., an LC plug at the end of a fiber optic cable,can be plugged into an adapter on a panel of an optical cassette tooptically couple directly with the lens at the end of the embeddedoptical fiber, such as an LC receptacle connector, inside of thecassette enclosure. The elimination of conventional connectors insidethe cassette significantly reduces the overall costs because iteliminates the highly skilled labor normally associated with terminatingan optical fiber to a connector, including polishing and epoxying thefiber into the connector, as well as the labor and craft dependenciesassociated with routing optical fibers inside a cassette. It furtherallows the cassette to be made very thin. Further, the flexible opticalcircuit in accordance with the present invention need not be placed in arigid housing or any housing at all, depending on the particularapplication.

Since the lensed flexible optical circuit is mechanically flexible, theconcept of the present invention can be used in many differentapplications, of which an optical cassette is merely one example. Forinstance, it can be placed in an L-shaped housing and used to make rightangle connections, such as a right angle optical wall adapter. It may bewound into a cylinder and used to make interconnections in existingconduit. The lensed flexible optical circuit connectivity concept can beincorporated into flexible housings, such as housings made of rubber sothat a single cassette can be used to make connections in differentenvironments and/or can compensate in all six degrees of freedom (e.g.,X, Y, and Z axes and roll, pitch, and yaw) to compensate for any form ofmisalignment of two components that are to be optically interconnected.Due to the flexible nature of the flexible optical circuit substrate,the invention can accommodate virtually any physical environment inwhich the interconnection fibers are not coplanar. As just noted, theflexible optical circuit can be bent into any non-planar shape,including, but not limited to, a cylinder, an S curve, a right anglecurve, a compound curve, and corrugations.

The invention further can be incorporated into housings having two partsinterconnected by a hinge so that they are bendable about the axis ofthe hinge to provide similar flexibility.

It is envisioned that a finite number of flexible optical circuits inaccordance with the present invention combined with a finite number ofmodularly connectable housing components, particularly flexible,bendable, stretchable, and/or hingedly connectable housing components,and one or more different lens blocks can offer the ability to modularlyconstruct an optical interconnect for virtually any situation from arelatively small number of pieces. Such a modular system wouldsubstantially reduce costs and substantially increase quality andrepeatability by substantially reducing or eliminating the human laborinvolved in fabricating such optical interconnection circuits.

FIG. 2 shows a flexible optical circuit 250 in accordance with theprinciples of the present invention. This particular flexible opticalcircuit achieves the same signal routing as the cassette in FIG. 1.Particularly, an optical fiber cable, such as cable 103 in FIG. 1 on theright side containing twelve fibers that need to be routed, one each tothe twelve single optical connectors, such as connectors 113 in FIG. 1on the left. Thus, the flexible optical circuit 250 includes twelveoptical fibers 217 routed accordingly. All of the embedded fibers 217are terminated at each end with a molded lens 230. The lenses 230 aredisposed in a lens block 257, which can be mounted in a separate holder(not shown in FIG. 2) as discussed in more detail below in connectionwith FIG. 4.

Flexible optical circuits are known and, hence, will not be described indetail. However, they essentially comprise one or more fibers 217sandwiched between two or more flexible sheets of material 226, 228,such as Mylar™ or another polymer. An adhesive 255 may be includedbetween two sheets in order to make them adhere to each other.Alternately, depending on the sheet material and other factors, the twosheets 226, 228 may be heated above their melting point to heat weldthem together with the fibers embedded between the two sheets.

Considerable technology has been developed relating to the design,fabrication, and use of such lenses in optical connectors, whichtechnology can be used to design and fabricate such lenses 230,terminate the optical fibers 217 with such lenses, and couple lightthrough such lenses to fibers in optical connectors. Such informationcan be obtained from the following patents and patent applications, allof which are incorporated herein fully by reference.

U.S. Pat. No. 7,722,261 entitled Expanded Beam Connector;

U.S. Pat. No. 8,085,472 entitled Expanded Beam Interface Device andMethod of Fabricating Same;

U.S. Pat. No. 8,313,249 entitled Multi-Fiber Ferrules for MakingPhysical Contact and Method of Determining Same;

U.S. Pat. No. 6,208,779 entitled Optical Fiber Array Interconnection;

U.S. Pat. No. 6,480,661 entitled Optical ADD/DROP Filter and Method ofMaking Same;

U.S. Pat. No. 6,690,862 entitled Optical Fiber Circuit;

U.S. Pat. No. 6,012,852 entitled Expanded Beam Fiber Optic Connector;and

U.S. Patent Publication No. 2012/0014645 entitled Single-Lens,Multi-Fiber Optical Connector Method and Apparatus.

More specifically, technology is available to couple a connectordirectly in front of the lens 230 so that the lens does not need to haveits own conventional mating connector, such as disclosed inaforementioned U.S. Pat. No. 7,722,261. Rather, with reference to FIG.3, which shows the flexible optical circuit 250 of FIG. 2 incorporatedinto an optical cassette 200 like that of FIG. 1, cables 103, 105 (orother optical components that are to be optically interconnected) can beterminated with conventional connectors 107, 109, as in FIG. 1. Theseconnectors 107, 109 may be plugged into adapters 115 on the cassette 200adjacent the respective lenses 230 and optically couple with the lenses(and, through the lenses, with the fibers 217 of the flexible opticallycircuit) without the need for a conventional second, mating connector onthe inside of the cassette housing 201.

With respect to the multiple fiber connector 107, each fiber mayoptically couple to an individual lens. However, alternately, a singlelarge lens 230 can be used to couple the light from each of the twelvefibers in connector 107 individually into the twelve fibers 217 on theflexible optical circuit 250. For instance, see U.S. Patent PublicationNo. 2012/0014645.

The use of the lensed flexible optical circuit 250 disclosed herein,therefore, eliminates most, if not all, of the skilled manual labornormally associated with fabricating an optical cassette. Particularly,polishing the end faces of the fibers. Furthermore, there is no need tomanually route optical fibers inside the cassette housing, which can bequite difficult when the number of optical couplings that need to bemade is large. Flexible optical circuits, on the other hand, aregenerally fabricated on substantially automated machines and thus can bemass produced quickly and inexpensively and then just inserted into ahousing.

The invention also eliminates many of the components employed inconventional internal connection and simplifies the connector process.This feature further reduces costs significantly as well as allows thehousing to be very thin and/or flexible.

FIG. 4 is a detailed exploded view of portion A of FIG. 3 illustratingthe interface of two fibers 217 in the flexible optical circuit 250 totwo fibers 271 in an exemplary two fiber external connector 109.Particularly, the external connector 109, which may be any conventionalconnector, such as an SC, LC, ST, or MPO connector, is inserted into anadapter 115 in an aperture in cassette housing 201 essentially in aconventional manner. On the internal side of housing 201, the flexibleoptical circuit 250 contains fibers 217, the end faces 217 a of whichare terminated to a lens block 257 comprising two lenses 230 molded aspart of a polymer block 258. Alternatively, the lenses can be fabricatedseparately and placed in openings in a supporting block, such as apolymer block. An index-matching material (not shown), such as a gel oradhesive, may be placed in the interstices between the end faces 217 aof the fibers of the flexible optical circuit 250 and the lenses 230 tominimize losses. Anti-reflective elements or coatings also may beinterposed to enhance optical return loss characteristics. The othersides of the lenses 230 are abutted to the adapter aligned with lightpaths 261 defined by the adapter, which, in turn, are aligned with theend faces of the optical fibers 271 in the external connectors 109.Again, an index matching material may be placed between the lenses 230and the adapters 115 and/or connectors 109.

The aforedescribed cassette embodiment is merely one embodiment of thepresent invention. In other embodiments, there may be no housing or thehousing may be flexible. For instance, connectors may be incorporatedinto the flexible optical circuits in other embodiments. Specifically,the lenses may be incorporated into conventional connectors mounted onthe flexible optical circuit which can then be mated to the opposingcomplementary connectors.

FIG. 5, for instance, illustrates an optical interconnect 500 inaccordance with the principles of the present invention being used tobreak out optical signals from a set of four multi-fiber connectors 501(each connector, in turn, comprising four fibers) to sixteen singlefiber connectors 503 in an equipment rack 505. Particularly, FIG. 5shows a portion of an equipment rack 505 containing a top row ofvertically oriented patch panels 509 and a bottom row of verticallyaligned patch panels 511. The top row of patch panels 509 comprises aplurality of vertically-oriented, dual-fiber connectors. The bottom rowof patch panels comprises a plurality of four slot, vertically-orientedpatch panels 511, each slot containing a connector having four fibers.

For each column, the breakouts from the bottom row of multi-fiberconnectors to the top row of single fiber connectors 503 areaccomplished by a series of flexible optical circuits 500 terminatedwith suitable connectors in accordance with the present invention. Forthis application, the opposing end faces of the fibers on flexibleoptical circuits 500 face in the same direction and are disposedadjacent the same edge of the flexible optical circuit or at leastsubstantially collinear edges of the flexible optical circuit.

In the prior art, these connections conventionally would be made withthe plurality of custom-made 1-to-4 cable assemblies with suitableconnectors at each end. Accordingly, making the interconnections in justone column would require a person to plug in sixteen (12+4) differentconnectors in what is likely to be a very tight space because,presumably, there are already other cables and connectors all around theconnections that need to be made. In addition, the rack very likely maybe in a data center comprising scores or hundreds of such racks closelypacked, making for a very cramped working environment.

Using the flexible optical circuit interconnector 500 of the presentinvention, those sixteen connections can be made simultaneously byproperly aligning the flexible optical circuit interconnector 500 of thepresent invention with the connectors on the appropriate patch panels509, 511 and pushing it in all at once to engage all sixteen connectorssimultaneously.

For this type of application, the flexible optical circuits can be maderigid enough to allow such pushing without crumpling of the flexibleoptical circuit, yet flexible enough to flex or stretch to account forany misalignment between the two patch panels 509, 511 involved in theconnection.

In other embodiments, a jig may be provided for supporting the flexibleoptical circuit 500 while it is being pushed in. Such a jig can be assimple as two parallel plates of plexiglass spaced apart from each otherenough to slip the flexible optical circuit 500 between the two plates,with the front end (the end including the connectors) sticking outslightly so that they can engage the mating connectors or adapters inthe patch panels 509, 511 while the majority of the flexible opticalcircuit is supported by the plates to prevent it from bending, folding,or mutilating.

FIG. 6 illustrates another use for the present invention in a rackdrawer. In the prior art, when optical cables are terminated to rackdrawers that can slide in and out of the rack telescopically, excesscable had to be provided hanging out of the back of the rack orentangled with adjacent cables or hardware so that there would be enoughexcess cable to allow the drawer to be pulled out without tensioning thecables.

In accordance with the present invention, the slack needed to allow thedrawers 600, 610 to slide in and out of the rack 602 can be providedwithin the drawer itself by using a flexible optical circuit 604 of thepresent invention within the drawer 600, 610 to interconnect the cables606 at the back panels 601, 611 of the drawers 600, 610 with the patchpanels 608, 609 at the fronts of the drawers. The flexible opticalcircuit 604 is made long enough to accommodate the drawer being pulledall the way out to its front stops, as shown with the upper left drawer600 in FIG. 6, but can fold up on itself to allow the drawer to bepushed all the way to its rear stops, as shown with the lower, righthand drawer 610 (note: fold 612).

In yet other embodiments, the flexible optical circuit and/or thehousing that it is embodied within may be corrugated in the manner of anaccordion so that the flexible optical circuit and its housing can bestretched and compressed longitudinally as well as bent into a compoundcurve. FIG. 7 illustrates a housing 701 constructed in accordance withsuch an embodiment. In such an embodiment, for instance, the front andback panels 705, 707 of the housing 701 bearing windows 702, 703 forreceiving adapters (also not shown) that will accept the connectors (notshown) of the optical components that will be optically connectedthrough the housing 701 may be made rigid, whereas the side walls 709,710, 711, 712 are made of a flexible material that can be folded andcompressed and stressed in the manner of an accordion, as illustrated.Alternately, the side walls may be telescopically expandable andcontractable.

The flexible optical circuit that will go on the housing 701 may becorrugated in a similar manner to that described above in connectionwith the housing 701 to make it extendible in length as well asbendable. However, alternately, the flexible optical circuit may beformed into an S shape along its length (as shown in FIG. 6—see 612) sothat the linear distance between its longitudinal ends and depths of thefolds can increase and decrease to accommodate the changing lineardistance between the opposite ends 705, 707 of the housing (andconsequently the linear distance between the opposing ends of thefibers) similarly to what is illustrated in FIG. 6. Care must be takenso as not to bend the optical fibers too sharply in the corrugations orS curves such that they might break or at least allow light to escapefrom the cores. However, many manufacturers now offer fibers that can bebent to very small radii curves without breakage or significant signalloss.

In yet other embodiments, such as illustrated in FIG. 8, the entirehousing 801 or at least the side walls 803, 804, 805, 806 (the wallsinterconnecting the panels 807, 808 that bear the apertures 809, 810 forreceiving the external connectors and/or adapters) may be made of aflexible material such as rubber so that the housing 801 can be bent toaccommodate situations in which the optical components to beinterconnected by the device cannot be longitudinally aligned.

FIG. 9 illustrates yet a further embodiment of a device 900 in which theflexible optical circuit 901 is incorporated into a housing 902 thatcomprises hinged members 904, 906. Specifically, housing 902 comprisestwo housing pieces 904, 906 joined at a hinge 905 so that the twohousing pieces 904, 906 may be disposed relative to each other atdifferent angular orientations about the hinge 905. While housing 902 isshown having an open configuration, it alternately could be closed, suchas by adding a third, curved housing member (not shown) inside of theother two members 904, 906 that encloses the internal space of thedevice 900 and that pieces 904, 906 can slide over as they pivot abouthinge 905 relative to each other.

The two lens blocks (not seen) may be disposed on the opposing end faces911, 912 of the housing 902. However, the illustrated embodiment shows amore adaptable configuration that further includes an additional panel907 connected to housing piece 904 via a second hinge 908. The lensblock 909 is mounted on the panel 907, which can be pivoted about hinge908 to provide additional freedom in positioning the ends of theflexible optical circuit relative to each other.

Situations in which the present invention is useful are bountiful. Forinstance, because there are no internal connectors, the flexible opticalcircuit interconnector of the present invention can be made very thin.Particularly, it may comprise a housing that, other than the end facesthat receive the external connectors, merely need be thick enough tohouse the flexible optical circuit (and accommodate any necessarycurvature thereof, such as corrugations or an S curve as mentionedpreviously). In fact, also as previously noted, in some embodiments,there may be no housing at all and adapters or other structure forreceiving the external connectors may be incorporated directly on theflexible optical circuit adjacent the end faces of the fibers and thelenses. Accordingly, it can be used for very low profile surface-mountedboxes for use in wall-mounted interconnects in office buildings, etc. Italso can be used for interconnects in modular furniture pieces, whichoften provide very small spaces for electrical or optical equipment.

Yet further, it is envisioned that a wide variety of opticalinterconnects can be made modularly from a relatively small number ofparts. Particularly, there would need to be a flexible optical circuitfor each different optical routing pattern type (e.g., 1-to-12 cablebreakout (such as illustrated in FIG. 2), 1-to-4 breakout, 1-to-4optical splitter, etc.) However, note that a single lensed flexibleoptical circuit could be used for various different numbers of suchbreakouts. For instance, a lensed flexible optical circuit in accordancewith the present invention that provides fiber routing for ten 1 to 4breakouts may be used in an optical cassette to provide anywhere fromone 1-to-4 breakout to ten 1-to-4 breakouts. If the cassette needs tooffer less than ten such breakouts, then some of the fibers/lensessimply are not used.

Since the lensed flexible optical circuits are flexible, they can bebent to accommodate many different physical layouts. The lensed flexibleoptical circuits may be constructed of a sufficient length toaccommodate most of the longest practical applications since they cansimply be folded up for the shorter applications. In cassette typeapplications or other applications involving a housing, a modular set ofmultiple housing pieces adapted to be modularly joined to each other invarious combinations may be provided. The housing components may providefor hinged and/or fixed joining. One or more of the housing componentsmay be flexible. Thus, it is possible to create almost any housing shapeand place one of the lensed flexible optical circuits within it. Thehousing components may include perture walls adapted to accept adaptersand/or connectors of any form factor.

While the invention has been described herein in connection embodimentsemploying molded lenses, it will be understood that this is merelyexemplary and that other optical components capable of guiding light maybe disposed at the ends of the fibers in the flexible optical circuits(or embedded in the laminate at the ends of the fibers) such.Light-guiding, fiber terminating optical components include, but are notlimited to, diffraction gratings, Escalier gratings, mirrors, andholograms.

It further should be understood that not all of the connections need tobe made at the opposing ends of the laminate strip. For instance, FIG.10 illustrates a flexible optical circuit 1001 in accordance with thepresent invention implemented as an optical splitter 1000. Such asplitter may be incorporated into a passive optical network (PON), forinstance. The lensed flexible optical circuit has an input connector1003 at one longitudinal edge of the flexible optical circuit 1001 andfive output connectors 1004 a-1004 e. Appropriate optical fibers 1009a-1009 e and lenses 1011 a-1011 f are disposed on the circuit 1001 inaccordance with the principles of the present invention as previouslydescribed to distribute the input signal received through inputconnector 1003 to the five output connectors 1004 a-1004 e. Four ofthose output connectors 1004 b-1004 e are located at the opposinglongitudinal edge of the flexible optical circuit, but one of the outputconnectors 1004 a is disposed in the middle of the flexible opticalcircuit 1001. In this particular exemplary embodiment, the lens 1011 aadjacent the middle output connector 1004 a is configured to operate asa splitter. For instance, it may be an expanded beam lens that increasesthe diameter of the beam received on input fiber 1009 a and couples itinto the four output fibers 1009 b-1009 e as well as directly intomiddle connector 1004 a. Additional lenses may be disposed in front ofthe output fibers 1009 b-1009 e in order to focus the beams back intothe output fibers. This intermediate point can be employed, forinstance, for monitoring signals or optical power in the circuit withoutinterrupting transmission in that device.

Yet further, the principles of the present invention can be used toreplace patch panels in equipment racks in data centers. Opticalinterconnections can be made in such a small, thin space using thepresent invention that such optical interconnects may be disposed inunoccupied air space within equipment racks that are otherwise fullyoccupied so as to provide even more dense optical interconnections inexisting equipment racks.

In yet other embodiments, electrically conductive wires also may beembedded within the flexible optical circuit along with the opticalfibers in order to provide both electrical and optical connectivity inone device. Applications with a need for combined optical and electricalconnectivity abound, such as power over Ethernet applications and out ofband signaling applications, such as disclosed in U.S. Pat. No.7,433,915.

Having thus described particular embodiments of the invention, variousalterations, modifications, and improvements will readily occur to thoseskilled in the art. Such alterations, modifications, and improvements asare made obvious by this disclosure are intended to be part of thisdescription though not expressly stated herein, and are intended to bewithin the spirit and scope of the invention. Accordingly, the foregoingdescription is by way of example only, and not limiting. The inventionis limited only as defined in the following claims and equivalentsthereto.

What is claimed is:
 1. A flexible optical circuit comprising: a flexiblesubstrate physically supporting a plurality of optical fibers extendingtoward light-guiding, fiber termination optical elements, wherein eachlight-guiding, fiber termination optical element terminates one of theoptical fibers supported by the flexible substrate, and wherein thelight-guiding, fiber termination optical elements are configured suchthat each of the light-guiding, fiber termination optical elements canoptically mate with a second optical connector for establishing anoptical signal therebetween, the light-guiding, fiber terminationoptical elements having a different format than the second opticalconnectors.
 2. A flexible optical circuit according to claim 1, whereinthe flexible substrate is positioned at least partially within acassette, wherein the cassette has a housing that defines a front sideand a rear side, wherein a first optical connector is coupled to thecassette housing, the first optical connector terminating a cablecarrying the plurality of optical fibers that are physically supportedby the flexible substrate, the plurality of optical fibers extendinginto the interior of the cassette housing from the first opticalconnector, the first optical connector positioned at the rear side and aplurality of optical adapters for mating the light-guiding, fibertermination optical elements and the second optical connectorspositioned at the front side of the housing with the flexible substratepositioned therebetween.
 3. A flexible optical circuit according toclaim 2, wherein the flexible substrate is configured to allow bendingin a direction generally perpendicular to a direction extending from thefront side to the rear side of the cassette housing.
 4. A flexibleoptical circuit according to claim 1, wherein each second opticalconnector includes an optical ferrule and each light-guiding, fibertermination optical element is selected from the group consisting of alens, a diffraction grating, an Escalier grating, a mirror, and ahologram.
 5. A flexible optical circuit according to claim 1, whereineach second optical connector is a conventional optical connectorselected from the group consisting of an SC connector and an LCconnector.
 6. A flexible optical circuit according to claim 2, whereinthe first optical connector is an MPO connector.
 7. A flexible opticalcircuit according to claim 1, wherein the plurality of optical fibersincludes at least twelve optical fibers.
 8. A flexible optical circuitaccording to claim 2, wherein end faces of each of the optical fibersextending from the first optical connector and supported by the flexiblesubstrate are terminated into a polymer block adjacent the plurality ofoptical adapters.
 9. A flexible optical circuit according to claim 1,wherein the light-guiding, fiber termination optical elements arephysically mounted on the flexible substrate.
 10. A flexible opticalcircuit according to claim 2, wherein both the second optical connectorsand the first optical connector include optical ferrules.
 11. A flexibleoptical circuit according to claim 1, wherein the flexible substratecomprises a laminate having first and second layers, and wherein theplurality of optical fibers are between the first and second layers. 12.A flexible optical circuit according to claim 1, wherein the flexiblesubstrate has a front longitudinal end and a rear longitudinal end and alength therebetween and is formed into a S-curve along its length suchthat the flexible optical circuit substrate can fold upon itself toalter the distance between the front longitudinal end and the rearlongitudinal end.
 13. A flexible optical circuit according to claim 1,wherein the flexible optical circuit is non-planar.
 14. A flexibleoptical circuit according to claim 5, wherein the light-guiding, fibertermination optical elements are not any of an SC connector, an LCconnector, an ST connector, or an MPO connector.